Q: What have you learned so far?
A: As you can imagine, we have weeks of footage to analyze every year. When we started the study in 2015, a colleague at the San Diego Zoo Wildlife Alliance logged the footage. But that was incredibly time-intensive, so in 2021, we worked with a San Diego Zoo programmer on a machine-learning system that can go through all the data in a short amount of time, logging where there is footage with polar bears in it.
After we know where to look, Joanna Sulich, who is based in Svalbard, analyzes the logged footage, recording metrics such as the number of cubs, the health and body condition of both moms and cubs, their behavior around the den site, and how long they hang around the den before departing for the sea ice. We now have enough data to publish results and, in fact, are working on a paper that we plan to publish later this year.
Among our findings, aside from metrics, we’ve documented that polar bear moms emerge from their dens earlier than indicated by collar data. Additionally, before the family emerges from the den, polar bear moms begin peeking out of the den for short periods of time. After the mom heads outside, her cubs follow, but only on warmer days, and they remain close to the den. After the cubs begin emerging more often, and presumably start feeling more comfortable with their surroundings, they start to increase the distance from the den and their mother.
Q: What about the related den-detection project? Any findings yet?
A: We are testing two different types of radar to see if they can find dens under the snow. One is synthetic aperture radar, or SAR, which can be mounted to a small aircraft, a project in partnership with Brigham Young University and Simon Fraser University. The other is a wide-band radar that can be mounted to a drone, a project in partnership with the Norwegian Polar Institute and NORCE. While both methods appear promising, more work needs to be done. Developing technology to pinpoint den locations is needed in order to protect polar bears from human activity, as the current method used, FLIR, misses more than half of known dens.
We tested SAR in Svalbard in 2022 and the wide-band radar in 2023. This year, if the weather and logistics permit, we plan to test the ability of the wide-band radar to detect an unoccupied dens. Future plans call for testing both in Alaska, where more human activity takes place and where the terrain is quite different from the steep slopes of Svalbard.
Q: Why does it take so long to learn anything from studies like these?
A: When studying behavior like denning, long-term studies are important because we are looking at an animal with a long lifespan. If we look at just one, two, or five years of a bear’s life, we get a very incomplete picture. Polar bears could have low—or high—birth rates for several years in a row, then completely reverse for the following 10 years. Polar bears require what we call a longitudinal study lest we make premature conclusions about them. The same holds true for monitoring the family’s body condition, the number of cubs, and so on. You need a long data set.
With the den-detection work, you also need a robust data set, under different conditions and on different terrain, to fully assess the effectiveness.
Q: What are your future plans for the project?
A: We plan to continue with this research in Svalbard, a part of the Arctic with rapid environmental change. A long data set there will provide critical information on the impact of these changes on moms and cubs. In addition, we are considering expanding the study to other areas, including Canada and Alaska.
Q: Is there anything else you’d like to add?
A: In Svalbard, we are constantly surprised about where the bears choose to den. To anyone who knows snowy mountains and the danger of steep slopes and avalanches, it’s amazing to see how frequently the bears perch themselves in fairly precarious places. For a cub coming out of the den for the first time, he’d better know how to use his brakes! It’s remarkable how polar bear moms have figured out how to den on these steep slopes and then lead their young cubs to the sea ice. The more I learn about polar bears, the more amazed I am.
Special thanks to Berlin Zoo, Natural World Safaris, Ouwehands Zoo, Saint Louis Zoo, Seneca Park Zoo, Svalbards Miljøvernfond, and Tierpark Berlin for helping to underwrite this project.